The purpose of this project is to study the physical properties of a wide variety of biological macromolecules with the goal of correlating these properties to the structure and function of the macromolecules. The emphasis is on the thermodynamics of the interactions of these macromolecules and on their molecular size and shape. Analytical ultracentrifugation and mathematical modeling are the principal research techniques used. Studies on the association of fibrinogen with other proteins involved in blood clotting and fibrinolysis have been continued. Studies in progress in this area deal with the association of fibrinogen with plasma and platelet Factor XIII and with the association of plasminogen with the D and E fragments of fibrinogen. Studies on synapsin have been directed toward determining the nature of the reactions involved in the self-association of this protein.